[iPhone 4] Half working microphone?

Hi all

I have an iPhone 4 32GB black.
But i seem to have some problems with the microphones.
When i record a video with the iPhone, and play the video, all sound is perfect.
But when i use Voice Recorder to record sound, and play this, i am only getting a high pitch buzzing sound.
The same problem appears with skype testing service.
Recording message, playback, high pitch buzz.

This is pretty annoying.

Does anyone knows what this might be, and where to start when solving the problem?

Thanks in advance.
Cheers,
minibike12